The more you use your smartphone, the less you sleep.
That’s according to a study released Wednesday by researchers at UC San Francisco, who used data from the university’s ongoing Health eHeart Study, which includes tens of thousands of participants and uses smartphone apps, ECG smartphone cases and portable blood pressure cuffs to track cardiovascular data.
Specifically, the study found that smartphone use directly impacts sleep, and those who use smartphones more often experience greater difficulty sleeping.
The smartphone versus sleep study specifically used a volunteer pool of 653 people with an average age of 42, and measured their smartphone screen time between Sept. 1, 2014, and Sept. 30, 2015.
To measure how smartphone use correlates with sleep, participants used an app for Android-based smartphones that recorded continuous screen time based on how many minutes in each hour the screen was on, provided the app was on and the phone wasn’t in airplane mode. Data was then transmitted each day to the study database.
“Our study found that, not surprisingly, people spend a lot of time interacting with their phones,” the study’s senior author Dr. Gregory Marcus, a UCSF Health cardiologist and director of clinical research in the UCSF Division of Cardiology, said in a statement.
“This was the first study to examine such use in a broad population, directly measuring screen time rather than relying on self-reported use,” he said. “And, those with more screen time use had poorer sleep.”
The study found that participants looked at their smartphones for nearly 39 hours in selected 30-day windows, which amounted to an average of 3.7 minutes of looking at a smartphone per hour. Younger participants and those who identified as black, Hispanic or “other” race/ethnicity used their smartphones more, according to the study.
The study appeared online Wednesday in PLOS ONE.